Water treatment apparatus and method

ABSTRACT

It is an object of the invention to provide an effective technique for detecting the quality of water with high accuracy. A representative water treatment apparatus includes an aerobic treatment region that treats water aerobically, a downstream region in which the water aerobically treated in the aerobic treatment region flows, a water quality sensor that is submerged in the downstream region and detects the water quality and a sensor washing arrangement that washes the water quality sensor by supplying the water of the downstream region to the water quality sensor at a flow rate higher than water flowing around the water quality sensor. As a result, sludge generated due to aerobic treatment can be prevented from being deposited on the water quality sensor and/or deposited sludge can be removed, so that the accuracy of water quality detection of the water quality sensor can be enhanced.

This is a continuation of U.S. patent application Ser. No. 11/594,970,filed Nov. 9, 2006, now U.S. Pat. No. 7,455,775.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique for treating water to betreated and more particularly, to an effective technique for washing awater quality sensor that detects the water quality.

2. Description of the Related Art

According to known water treatment apparatus for treating water, waterquality is detected by using a water quality sensor. For example,Japanese laid-open patent publication No. 3-52696 discloses a watertreatment apparatus of this type in which a DO sensor is provided in anaeration tank disposed upstream of a sterilizing tank in a submergedstate. The quality of the aerated water can be kept track of by the DOsensor.

The water quality sensor is submerged in a purifying region to detectthe water quality and therefore, an accuracy of water quality detectiontends to be impaired by deposition of biomembrane on the sensor surface.In this connection, the water quality sensor is preferably installedparticularly in a downstream region in which aerobically treated waterflows. However, if the water quality sensor is installed downstream ofthe aerobic treatment region, sludge is generated due to aerobictreatment and deposited on the sensor surface. Therefore, it becomesdifficult to enhance the accuracy of water quality detection to adesired level.

SUMMARY OF THE INVENTION

It is, accordingly, an object of the invention to provide an effectivetechnique for detecting the quality of water with high accuracy.

A representative water treatment apparatus according to the presentinvention includes at least an aerobic treatment region, a downstreamregion, a water quality sensor and a sensor washing arrangement.

The aerobic treatment region according to the invention is designed as aregion in which water is aerobically treated. The aerobic treatment isdefined as a treatment of decomposing organic pollutant in the water tobe treated by aerobic microbes in the presence of dissolved oxygen. Theaerobic treatment region for such aerobic treatment may preferably bedesigned as a “contact filter bed tank” packed with contact materials onwhich biomembrane of aerobic microbes is deposited and with filter mediafor Filtration, or as a “carrier flow biofiltration tank” having movablypacked carriers on which biomembrane of aerobic microbes is deposited.

The downstream region is designed as a region in which water aerobicallytreated in the aerobic treatment region flows. In the downstream region,the aerobically treated water may preferably be subjected to furtherpurification or to transfer or storage. The aerobic treatment region andthe downstream region may preferably be defined by dividing the waterstorage section by a partition or by the function even in the absence ofthe partition. For example, in a single treatment tank (treatmentsection), only an area in which dissolved oxygen exists due to airdiffusion can be defined as the aerobic treatment region.

The water quality of the downstream region is detected by the waterquality sensor that is submerged in the downstream region. The “waterquality sensor” here may preferably includes a detecting part itself(sensor surface) that performs substantial water quality detection, orthe detecting part plus a sensor housing for housing the detecting part.As the water quality detection sensor, various kinds of sensors can beappropriately used to detect data relating to the water quality, such asturbidity, transparency, SS (suspended solids), BOD (biochemical oxygendemand), DO (dissolved oxygen), pH, and UV (ultraviolet) absorbance ofthe water, continuously or at fixed time intervals.

Further, according to the invention, a sensor washing arrangement isprovided for washing the water quality sensor. The sensor washingarrangement washes the water quality sensor by supplying the water ofthe downstream region to the water quality sensor at a flow rate higherthan water flowing around the water quality sensor. The “washing” heremay preferably include the manner of preventing deposition of sludge onthe water quality sensor by the force of water and/or the manner ofblowing away and removing sludge deposited on the water quality sensorby the force of water. This construction is rational in that water ofthe downstream region to be detected by the water quality sensor is usedin itself for washing the water quality sensor without any anotheradditional washing equipment.

By using such sensor washing arrangement, sludge generated due toaerobic treatment can be prevented from being deposited on the waterquality sensor and/or deposited sludge can be removed, so that theaccuracy of water quality detection of the water quality sensor can beenhanced. Further, such construction can dispense the need for providinga washing mechanism in the water quality sensor itself and is thuseffective in simplifying the structure of the water quality sensor. Thewater of which flow rate is increased by the sensor washing arrangementmay preferably be supplied to the water quality sensor continuously orintermittently (discontinuously).

Other objects, features and advantages of the present invention will bereadily understood after reading the following detailed descriptiontogether with the accompanying drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows the construction of a water treatmentapparatus 100 according to a first representative embodiment of thepresent invention.

FIG. 2 shows a further detailed construction of a sterilizing tank 150as shown in FIG. 1.

FIG. 3 shows a detailed construction of a sterilizing tank 250 as analternative to the sterilizing tank 150 as shown in FIG. 1.

FIG. 4 schematically shows the construction of a water treatmentapparatus 30Q according to a second representative embodiment of thepresent invention.

FIG. 5 shows a further detailed construction of a discharge pump tank180 as shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Each of the additional features and method steps disclosed above andbelow may be utilized separately or in conjunction with other featuresand method steps to provide and manufacture improved water treatmentapparatus and method for using such water treatment apparatus anddevices utilized therein. Representative examples of the presentinvention, which examples utilized many of these additional features andmethod steps in conjunction, will now be described in detail withreference to the drawings. This detailed description is merely intendedto teach a person skilled in the art further details for practicingpreferred aspects of the present teachings and is not intended to limitthe scope of the invention. Only the claims define the scope of theclaimed invention. Therefore, combinations of features and stepsdisclosed within the following detailed description may not be necessaryto practice the invention in the broadest sense, and are instead taughtmerely to particularly describe some representative examples of theinvention, which detailed description will now be given with referenceto the accompanying drawings.

An embodiment of the present invention will now be explained withreference to the drawings. This embodiment provides a water treatmentapparatus for treating domestic wastewater.

FIRST REPRESENTATIVE EMBODIMENT

FIG. 1 schematically shows the construction of a water treatmentapparatus 100 according to a first embodiment of the present invention.As shown in FIG. 1, the water treatment apparatus 100 includes variouspurifying mechanisms within a tank body 101. Specifically, the tank body101 houses, from the upstream side (left to right as viewed in FIG. 1)in order of the treatment procedures, a foreign matter removing tank110, an anaerobic filter bed tank 120, a contact filter bed tank 130, atreated water tank 140 and a sterilizing tank 150. “Inflow water” in theform of wastewater flows into the tank body 101 and is purified withinthe foreign matter removing tank 110, the anaerobic filter bed tank 120,the contact filter bed tank 130, the treated water tank 140 and thesterilizing tank 150 successively. Thereafter, the treated water isdischarged as “outflow water” to the outside of the tank body 101. Inthis embodiment, the “water to be treated” or “water” includeswastewater to flow from outside into the tank body 101, wastewater to betreated in each tank within the tank body 101 and water that flows inthe process of treating the wastewater.

Foreign matter removing tank 110 is disposed in the most upstreamportion of the tank body 101. Water to be treated flows into the foreignmatter removing tank 110 through an inlet (not shown). Foreign matter inthe water is separated from the water in the foreign matter removingtank 110 by means of a solid-liquid separating device such as an inflowbaffle (not shown). The foreign matter removing tank 110 has a functionof separating solid from liquid in the water to be treated. The waterthat has been treated in this foreign matter removing tank 110 is thentransferred to the anaerobic filter bed tank 120 disposed downstream ofthe foreign matter removing tank 110.

Anaerobic filter bed tank 120 has a function of anaerobically treating(reducing) organic pollutant in the water to be treated. Typically, theanaerobic filter bed tank 120 is configured to have a filter bed packedwith a predetermined amount of filter media. Anaerobic microbes aredeposited on the filter media and anaerobically treat (reduce) organicpollutant in the water. Reduction of BOD and weight reduction of sludgecan be attained by this anaerobic treatment. The treated water isthereafter transferred to the anaerobic filter bed tank 120 disposeddownstream of the contact filter bed tank 130.

Contact filter bed tank 130 has a function of aerobically treating andfiltering the water. In a path through which water to be treated flows,the contact filter bed tank 130 has a contact materials packed regionpacked with contact materials on which biomembrane of aerobic microbesis deposited, an air diffuser that supplies air to the contact materialsin the contact materials packed region, and a filter media packed regionpacked with filter media for filtration. When air is supplied from theair diffuser, aerobic microbes deposited on the contact materials in thecontact materials packed region contact the water to be treated, so thatorganic pollutant in the water to be treated is mainly aerobicallytreated (oxidized). The contact materials packed region of the contactfilter bed tank 130 is a feature that corresponds to the “aerobictreatment region” according to this invention. Further, the treatedwater tank 140 and the sterilizing tank 150 which are disposeddownstream of the aerobic treatment region or the contact filter bedtank 130 is a downstream region through which the water treated in theaerobic treatment region flows, and forms the “downstream region” inthis invention.

Further, SS (suspended solids) within the water is filtered by thefilter media in the filter media packed region. The water that has beentreated in the contact filter bed tank 130 is transferred downstream tothe treated water tank 140.

Treated water tank 140 has a function of temporally storing the water tobe led into the sterilizing tank 150. The water temporally stored in thetreated water tank 140 is transferred downstream to the sterilizing tank150.

Sterilizing tank 150 has a function of sterilizing the water that hasbeen led from the treated water tank 140. In this embodiment, thesterilizing tank 150 is positioned in the most downstream portion withinthe tank body 101. A chemical cartridge (a chemical cartridge 152 whichwill be described below with reference to FIG. 2) is disposed in themost upstream portion of the sterilizing tank 150 and filled with asolid chlorinating agent (antiseptic). The water that has beensterilized in this sterilizing tank 150 is discharged to the outside ofthe tank body 101. Specifically, the sterilizing tank 150 forms asterilizing region for sterilizing the water aerobically treated in theaerobic treatment region or the contact filter bed tank 130, and is afeature that corresponds to the “sterilizing region” according to thisinvention.

In this embodiment, a water quality sensor 160 is submerged in asubmerged region (a submerged region 151 which will be described belowwith reference to FIG. 2) of the sterilizing tank 150. The water qualitysensor 160 has a function of detecting (also referred to as “measuring”)the quality of sterilized water and has a detecting section (a detectingsection 162 which will be described below with reference to FIG. 2) thatis disposed within a sensor housing and substantially performs detectionof the water quality. In this embodiment, the installation of the waterquality sensor 160 in the sterilizing tank 150 in which the wateraerobically treated in the contact filter bed tank 130 flows, isparticularly effective in reducing deposition of biomembrane on thedetecting section (the detecting section 162) of the water qualitysensor 160. The water quality sensor 160 and the detecting section(detecting section 162) of the water quality sensor 160 respectivelycorrespond to the “water quality detection sensor” according to thisinvention.

In this embodiment, the water quality sensor 160 typically comprises aoptical turbidity measurement sensor (or transparency measurementsensor) employing a transmitted light system utilizing red light or nearinfrared radiation, or a scattered light system utilizing red light ornear infrared radiation, in order to detect the turbidity (ortransparency) of the sterilized water. Further, if the influence of thesterilizing treatment is considered, the sensor housing of the waterquality sensor 160 may preferably comprise corrosion-resistant SUS(stainless steel) or resin material.

FIG. 2 shows a further detailed construction of the sterilizing tank 150shown in FIG. 1. As shown, water containing chloride components issupplied from the chemical cartridge 152 into a tub 153 and stored inthe tub 153. Thereafter, the water falls from the tub 153 through adischarge section 154 into the submerged region 151 in which the waterquality sensor 160 is submerged.

In this submerged region 151, in addition to the water quality sensor160, an air lift pump 170 is installed. The air lift pump 170 isdesigned specifically for cleaning the water quality sensor 160 andincludes at least a pump body 172, a pump intake section 174, a pumpdischarge section 176 and an air supply section 178. The pump body 172extends vertically in the tank. The pump intake section 174 is formed onthe bottom of the pump body 172 and water in the submerged region 151 ispumped up through the pump intake section 174. The pump dischargesection 176 is formed above the pump intake section 174 in the pump body172, protrudes laterally from underwater and is designed as a partthrough which the water pumped up through the pump intake section 174 isdischarged. When air is supplied from an air supply source such as ablower into the pump body 172 via the air supply section 178, air flowsupward in the pump body 172 of the air lift pump 170. With such airflow, water in the submerged region 151 is pumped up through the pumpintake section 174 and discharged through the pump discharge section176.

Particularly in this embodiment, the relative position of the pumpdischarge section 176 of the air lift pump 170 and the water qualitysensor 160 can be appropriately adjusted such that the pump water isdischarged toward the detecting section 162 of the water quality sensor160.

With this construction of the air lift pump 170, the water dischargedfrom the pump discharge section 176 of the air lift pump 170 can besupplied to the detecting section 162 by the force of the dischargedwater at a flow rate higher than the water flowing around the detectingsection 162 of the water quality sensor 160. As a result, the surface ofthe detecting section 162, or the sensor surface comprising a lightemitting section 162 a and a light receiving section 162 b can bewashed, so that deposition of sludge on the sensor surface can beprevented by the force of the discharged water, or sludge deposited onthe sensor surface can be blown away and removed by the force of thedischarged water. In this manner, the detecting section 162 can bewashed while being kept from being contaminated. Specifically, in thisembodiment, the discharge energy (kinetic energy) of the waterdischarged from the pump discharge section 176 of the air lift pump 170can be utilized to wash the detecting section 162 or the sensor surface.

With this construction, contamination of the detecting section 162 canbe prevented by the action of the water discharged from the pumpdischarge section 176 of the air lift pump 170 and allows the waterquality sensor 160 to properly perform water quality detection. In thisconstruction, the water of which flow rate is increased by the air liftpump 170 may be supplied to the detecting section 162 continuously orintermittently (discontinuously). Particularly with the construction inwhich the water having a flow rate increased by the air lift pump 170 isintermittently supplied to the detecting section 162, a higher effect ofwashing the detecting section 162 can be obtained. Further, thisconstruction is rational in that the water in the submerged region 151(the sterilizing tank 150) to be detected by the detecting section 162is used in itself for washing the detecting section 162. The air liftpump 170 is a feature that corresponds to the “sensor washingarrangement” and the “pumping device” according to this invention.

Further, with this construction of the air lift pump 170, water withinthe sterilizing tank 150 is stirred by the force of the water dischargedfrom the pump discharge section 176. As a result, the water qualitywithin the sterilizing tank 150 can be homogenized, so that the waterquality sensor 160 can perform stable water quality measurement.Further, in order to enhance the stirring effect of the water dischargedfrom the pump discharge section 176, as necessary, a baffle or the likemay be appropriately installed within the sterilizing tank 150.

Further, with regard to the construction of the water quality sensor 160in this embodiment, preferably, the sensor surface of the detectingsection 162 is oriented to extend in a direction crossing the directionof discharge of the water to be discharged from the pump dischargesection 176. In this construction, the orientation of the sensor surfaceof the water quality sensor 160 may be adjusted according to thedirection of discharge from the pump discharge section 176, or viceversa. With this construction, the discharge energy of the waterdischarged from the pump discharge section 176 can be efficiently causedto act upon the sensor surface of the detecting section 162, so that thedetecting section 162 can be washed by stronger water force.

Further, the water quality sensor 160 in this embodiment is preferablyconstructed such that the sensor surface of the detecting section 162 issmoothed. The smoothing of the sensor surface can be achieved bysmoothing the sensor surface itself, or by covering the sensor surfacewith a coating or by applying a film having a high smoothness to thesensor surface. Further, in the water quality sensor 160 in thisembodiment, preferably, the sensor surface may comprise translucentmaterials having a smooth surface, such as glass or sapphire glass, orother translucent materials (such as acrylic resin). With suchconstruction, the transmittance of the water quality sensor 160 isensured so that the detecting performance is maintained. In addition,the sensor surface is smoothed so that deposition of sludge on thedetecting section 162 can be reduced. Therefore, in cooperation with theforce of the water discharged from the pump discharge section 176 of theair lift pump 170, such construction can further enhance the effect ofwashing the detecting section 162. Particularly by using sapphire glassfor the sensor surface, the sensor surface can be rendered more scratchresistant compared with that of glass. Further, by using acrylic resinfor the sensor surface, the construction can be cheaper compared withthat of glass.

Further, as an alternative or in addition to such smoothing, the sensorsurface may be fluorinated or covered with a photocatalytic coating. Asfor fluorination, a surface preparation agent containing fluorocarbonpolymer is applied to the sensor surface. Thus, the water or oilrepellency of the sensor surface can be enhanced, so that deposition ofsludge on the detecting section 162 can be reduced. As for aphotocatalytic coating, the sensor surface is covered with a titaniumoxide film and the titanium oxide film is subjected to light. As aresult, oxidative decomposition of sludge and superhydrophilic action oflifting the dirt and washing it away can be caused, so that depositionof sludge on the detecting section 162 can be reduced. In this case,preferably, the surface preparation agent and the titanium oxide filmare transparent and colorless so as to hardly influence the opticalcharacteristics.

Further, with regard to the construction of the water quality sensor 160in this embodiment, in order to detect the standard quality ofsterilized water with high accuracy, in consideration of precipitatedsludge that is precipitated in the bottom of the sterilizing tank 150,or suspended sludge that is suspended in the water surface in the tanktop, preferably, the detecting section 162 of the water quality sensor160 is disposed between the precipitated sludge region and the suspendedsludge region within the submerged region 151 of the sterilizing tank150 in its vertical direction. With this construction, influence ofprecipitated sludge and suspended sludge on the water quality detection(measurement) of the water quality sensor 160 can be avoided. Thus, thestandard quality of sterilized water can be detected with stability andhigh accuracy.

Further, with regard to the construction of the water quality sensor 160in this embodiment, the water quality sensor 160 may preferably beoriented such that precipitated sludge is not easily precipitated on thedetecting section 162, in consideration of the configuration andstructure of the detecting section 162. For example, if the sensorsurface of the detecting section 162 is flat, the water quality sensor160 may be installed in the orientation in which the sensor surfaceextends vertically. Thus, the sludge that has been precipitated downwardin the water is not easily deposited on the detecting section 162 of thewater quality sensor 160, so that a stable water quality measurement canbe achieved with the water quality sensor 160.

Bubbles (air) flow up within the pump body 172 and is discharged to theoutside of the pump through the pump discharge section 176. Preferably,the air lift pump 170 of this embodiment is constructed such that thedischarged bubbles move upward directly toward the tank top in such amanner as to avoid contact with the detecting section 162 as shown inFIG. 2. Such contact avoidance can be achieved by appropriatelyadjusting the distance between the pump discharge section 176 of the airlift pump 170 and the detecting section 162 of the water quality sensor160. Specifically, the distance between the pump discharge section 176and the detecting section 162 can be adjusted such that the flow ofwater discharged from the pump discharge section 176 reaches thedetecting section 162 while the bubbles discharged from the pumpdischarge section 176 do not contact the detecting section 162. Withthis construction, occurrence of variations in the detected value of thewater quality sensor 160 can be prevented.

Further, with regard to the construction of the air lift pump 170 ofthis embodiment, the pump discharge section 176 can be appropriatelylocated under, around or over the water surface, and particularlypreferably, under or around the water surface. With this construction,compared with the case in which the pump discharge section 176 isarranged over the water surface, the use of air for pump transfer ofwater by the air lift pump 170 can be reduced by reducing the pump head.

The data detected continuously or at fixed time intervals by the waterquality sensor 160 are outputted to an output section 166 by means ofindication or voice via a cable 164. Thus, the quality of the watersterilized in the sterilizing tank 150 or the water to be discharged tothe outside of the tank body 101 can be controlled. Specifically, anindicator or an alarm is installed on or around the water treatmentapparatus 100 itself. The indicator displays the data, or the alarmnotifies that the water quality is not within the predetermined range oflevel, if such occurs. Alternatively or in addition, the detected dataof the water quality sensor 160 is appropriately transmitted by wire orradio channel via a terminal (not shown) to a data monitor (datamanagement system) or data processor which is installed in a positionremote from the water treatment apparatus 100.

It is known that water turbidity (or transparency) is generallycorrelated with BOD (biochemical oxygen demand) and SS (suspendedsolids). In this embodiment, it is constructed such that quantitative orqualitative analysis of water quality can be performed in relation toBOD and SS by obtaining detected turbidity (or transparency) data. Atthis time, the water quality detection sensor 160 may be constructedsuch that the detected turbidity (or transparency) data itself isoutputted as-is to the output section 166, or such that the detectedturbidity (or transparency) data is converted into data relating to BODor SS and the converted date is outputted to the output section 166.

Further, in this embodiment, the water quality detection sensor 160 isused to keep track of the sterilizing performance of the sterilizingtank 150 as well as the water quality detection as mentioned above. Ifthe sterilizing performance deteriorates, biomembrane will be depositedon the detecting section 162 of the water quality sensor 160, resultingin that the detected value of the water quality sensor 160 falls outsidethe normal range. Therefore, by monitoring the detected data, it can befound that the sterilizing performance has deteriorated, for example,due to shortage of the chlorinating agent. Thus, the water qualitysensor 160 of this embodiment not only serves as a means for detectingthe quality of water of the sterilizing tank 150, but also as a meansfor detecting that biomembrane has been deposited on the detectingsection of the water quality sensor 160 due to deterioration of thesterilizing performance of the sterilizing tank 150.

In the water treatment apparatus 100 in this embodiment, a sterilizingtank of different construction can be used in place of the sterilizingtank 150. FIG. 3 shows a detailed construction of a sterilizing tank 250as an alternative to the sterilizing tank 150 shown in FIG. 1.

In the sterilizing tank 250 shown in FIG. 3, the washing treatment ofthe water quality sensor 160 is achieved, without using the air liftpump 170, by utilizing the force of water to be dropped from thedischarge section 154 of the tub 153 in which the chemical cartridge 152is disposed, into a submerged region 251 in which the water qualitysensor 160 is submerged. Specifically, the detecting section 162 of thewater quality sensor 160 is positioned under the water surface in alocation within the submerged region 251 where the water discharged fromthe discharge section 154 falls. Further, a drop ΔH is provided betweenthe discharge section 154 and the water quality sensor 160 such that thedischarge height of the discharge section 154 is higher than theinstallation height of the water quality sensor 160. The waterdischarged from the discharge section 154 can be supplied to thedetecting section 162 by the force of the discharged water fallingtoward the detecting section 162 of the water quality sensor 160 at aflow rate higher than the water flowing around the detecting section 162of the water quality sensor 160. As a result, deposition of sludge onthe sensor surface (the light emitting section 162 a and the lightreceiving section 162 b) can be prevented by the force of the dischargedwater, or sludge deposited on the sensor surface can be blown away andremoved by the force of the discharged water. In this matter, thedetecting section 162 can be washed. Specifically, in this embodiment,the falling energy (potential energy) of the water discharged andfalling from the discharge section 154 can be utilized to wash thesensor surface (the surface to be washed) of the detecting section 162.

With this construction, the water quality sensor 160 is allowed toproperly perform water quality detection by prevention of contaminationof the detecting section 162 by the falling action of the waterdischarged from the discharge section 154. In this construction, thewater of which flow rate is increased by the falling action of the waterdischarged from the discharge section 154 may be supplied to thedetecting section 162 continuously or intermittently. Particularly withthe construction in which the water having an increased flow rate by thefalling action of the water discharged from the discharge section 154 isintermittently supplied to the detecting section 162, a higher effect ofwashing the detecting section 162 can be obtained. Further, thisconstruction is rational in that sterilized water itself to be detectedby the detecting section 162 is used for washing the detecting section162. The construction in which the water discharged from the dischargesection 154 falls toward the detecting section 162 of the water qualitysensor 160 forms the “sensor washing system” according to thisinvention.

Further, with regard to the construction of the water quality sensor 160in this embodiment, preferably, the sensor surface of the detectingsection 162 is oriented to extend in a direction crossing the directionof discharge (drop) of the water from the discharge section 154. In thisconstruction, the orientation of the sensor surface of the water qualitysensor 160 may be adjusted according to the direction of discharge fromthe discharge section 154, or vice versa. With this construction, thefalling energy of the water discharged and falling from the dischargesection 154 can be efficiently caused to act upon the sensor surface ofthe detecting section 162, so that the detecting section 162 can bewashed by stronger water force.

As described above, according to the construction of the water treatmentapparatus 100 and the water treatment method using the water treatmentapparatus 100 in the first embodiment, the detecting section 162 of thewater quality sensor 160 can be reliably washed by utilizing the forceof water discharged from the pump discharge section 176 of the air liftpump 170, or the force of water discharged and falling from thedischarge section 154 of the tub 153. Thus, the water quality sensor 160can attain higher accuracy of water quality detection. Further, sludgecontained in sterilized water has lower adhesion than that inunsterilized water and is thus less sticky or viscous and resistant toadhesion to the water quality sensor. Therefore, sludge or any otherdeposits can be further reliably prevented from being deposited on thedetecting section 162 of the water quality sensor 160 submerged in thesterilizing tank 150. Further, the construction which uses water forceto wash the detecting section 162 of the water quality sensor 160 candispense the need for providing a washing mechanism in the water qualitysensor 160 itself and is thus effective in simplifying the structure ofthe water quality sensor 160.

Further, according to the water treatment apparatus 100, not only thequality of water flowing within the tank body 101 but the quality ofwater to be discharged to the outside of the tank body 101 can beaccurately and constantly monitored. Particularly, as for domestic watertreatment apparatus for treating domestic wastewater, maintenance isless frequently performed (for example, every four months) compared withthose for industrial use. It is therefore highly desired to monitor thewater quality until the next maintenance is performed. Therefore, likein this invention, by constantly monitoring the quality of water to bedischarged to the outside of the tank body 101 by using the waterquality sensor 160, it is made possible to keep track of the performanceof the water treatment apparatus 100 and to promptly cope withdeterioration of the performance if any. Thus, the quality of water tobe discharged to the outside of the tank body 101 can be maintained andcontrolled into a desired state. Therefore, an environmentally friendlywater quality control can be realized.

Further, as described above, the water quality sensor 160 is used as ameans for detecting the water quality within the sterilizing tank 150and also as a means for detecting biomembrane deposition on thedetecting section 162 of the water quality sensor 160. Therefore, thewater quality sensor 160 can be used to monitor the water quality of thewater storing section and also to monitor the sterilizing performance.Thus, an efficient water quality control can be realized.

SECOND REPRESENTATIVE EMBODIMENT

FIG. 4 schematically shows the construction of a water treatmentapparatus 300 according to a second embodiment of the present invention.As shown in FIG. 4, in addition to the same purifying mechanisms as thewater treatment apparatus 100 of the first embodiment (the foreignmatter removing tank 110, the anaerobic filter bed tank 120, the contactfilter bed tank 130, the treated water tank 140 and the sterilizing tank150 or 250), the water treatment apparatus 300 further includes adischarge pump tank 180 within the tank body 101. The discharge pumptank 180 may be housed in the tank body 101 in which the other purifyingmechanisms are housed, or may be formed as a tank separate from the tankbody 101.

Discharge pump tank 180 is disposed downstream of the sterilizing tank150 and has a function of temporally storing the water sterilized in thesterilizing tank 150 and then discharging it to the outside of the tankbody 101. The discharge pump tank 180 is disposed downstream of theaerobic treatment region or the contact filter bed tank 130 and is adownstream region through which the water treated in the aerobictreatment region flows, and forms the “downstream region” in thisinvention. In this embodiment, the same water quality sensor 160 as usedin the sterilizing tank 150 or 250 of the water treatment apparatus 100is installed in the discharge pump tank 180. Therefore, detailedexplanation of the water quality sensor 160 will be omitted. In thisembodiment, installation of the water quality sensor 160 in thedischarge pump tank 180 in which the water aerobically treated in thecontact filter bed tank 130 flows is particularly effective in reducingdeposition of biomembrane on the detecting section (the detectingsection 162) of the water quality sensor 160.

FIG. 5 shows a further detailed construction of the discharge pump tank180 shown in FIG. 4. As shown, the discharge pump 190 is disposed in asubmerged region 181 of the discharge pump tank 180 together with thewater quality sensor 160 and designed as a “submerged pump” installedwith a pump body 191 of the discharge pump 190 submerged in the tank. Amotor 192 for driving a pump mechanism is disposed within the pump body191 of the discharge pump 190. When the pump mechanism is driven by themotor 192, water is pumped up from a pump intake section 193, ledthrough a vertically extending transfer tube 194 and then dischargedfrom a pump discharge section 195. The motor 192 is designed to becontrolled by a controller 198 based on the detected data of the waterlevel of the submerged region 181 which is detected by a water leverdetection sensor 197. The controller 198 may be designed exclusively forcontrolling the amount of pump discharge of the discharge pump 190, ormay be designed for controlling the entire spectrum of the watertreatment apparatus 100 as well as the pump discharge. Further, as thewater lever detection sensor 197, a float type level sensor, adifferential pressure type level sensor, ultrasonic or infrared levelsensor may be appropriately used.

With regard to the specific control of the motor 192, a construction ofswitching between drive control and stop control of the motor 192according to the water level and the water level change of the submergedregion 181, and a construction of increasing and decreasing the motorrevolutions of the motor 192 according to the water level and the waterlevel change of the submerged region 181, are appropriately used. Forexample, first and second constructions may be used. The firstconstruction controls the motor 192 to be driven at certain revolutionsonly when the water level of the submerged region 181 exceeds areference level, while controlling the motor 192 to be stopped when thewater level is lowered below the reference level. The secondconstruction controls the motor revolutions of the motor 192 to varysuch that the water level of the submerged region 181 is adjusted to theneighborhood of the reference level. With this construction, the amountof water to be discharged from the discharge pump tank 180 can be variedaccording to the operating duty of the treatment regions locatedupstream of the discharge pump tank 180 (the submerged region 181) inwhich the water quality sensor 160 is installed.

Particularly, the discharge pump 190 of this embodiment has a functionof discharging the water stored in the discharge pump tank 180, by pumptransfer, and also a function of washing the water quality sensor 160.Specifically, a branch pipe 196 is provided on the transfer tube 194 andextends laterally from the transfer tube 194. The branch pipe 196branches part of the water pumped up through the pump intake section193. In this embodiment, the relative position of the branch pipe 196 ofthe discharge pump 190 and the water quality sensor 160 can beappropriately adjusted such that the pump water is discharged from thebranch pipe 196 toward the detecting section 162 of the water qualitysensor 160.

The water discharged from the branch pipe 196 of the discharge pump 190can be supplied to the detecting section 162 by the force (flow) of thedischarged water at a flow rate higher than the water flowing around thedetecting section 162. As a result, deposition of sludge on the sensorsurface can be prevented by the force of the discharged water, or sludgedeposited on the sensor surface can be blown away and removed by theforce of the discharged water. In this manner, the detecting section 162can be washed while being kept from being contaminated. Specifically, inthis embodiment, the discharge energy (kinetic energy) of the waterdischarged from the branch pipe 196 of the discharge pump 190 can beutilized to wash the sensor surface (the surface to be washed) of thedetecting section 162.

With this construction, contamination of the detecting section 162 canbe prevented by the action of the water discharged from the branch pipe196 of the discharge pump 190 allowing the water quality sensor 160 toproperly perform water quality detection. In this construction, thewater of which flow rate is increased by the discharge pump 190 may besupplied to the detecting section 162 continuously or intermittently.Particularly with the construction in which the water having a flow rateincreased by the discharge pump 190 is intermittently supplied to thedetecting section 162, a higher effect of washing the detecting section162 can be obtained. Further, this construction is rational in that thewater in the submerged region 181 (the discharge pump tank 180) to bedetected by the detecting section 162 is used in itself for washing thedetecting section 162. The discharge pump 190 is a feature thatcorresponds to the “sensor washing arrangement” and the “pumping device”according to this invention. Further, the pump intake section 193 andthe branch pipe 196 of the discharge pump 190 are features thatcorrespond to the “pump intake section” and the “pump dischargesection”, respectively, according to this invention.

Further, water within the discharge pump tank 180 is stirred by theforce of the water discharged from the branch pipe 196. As a result, thewater quality within the discharge pump tank 180 can be homogenized, sothat the water quality sensor 160 can perform stable water qualitymeasurement. Further, in order to enhance the stirring effect of thewater discharged from the branch pipe 196, a baffle or the like may beappropriately installed within the discharge pump tank 180, asnecessary.

Further, the amount of water to be discharged from the discharge pumptank 180 can be varied according to the operating duty of the treatmentregions located upstream of the discharge pump tank 180 (the submergedregion 181) in which the water quality sensor 160 is installed. Thus,the amount of water to be discharged from the branch pipe 196 can alsobe varied according to the operating duty of the upstream regions. Thisoperating duty can be kept track of from the amount or the change of theamount of water flowing in the treatment regions located upstream of theinstallation location of the water quality sensor 160 and from the waterlevel or the change of the water level of the treatment regions. Inflowof sludge which may possibly be deposited on the detecting section 162of the water quality sensor 160 is assumed to increase as the operatingduty increases.

Therefore, according to this embodiment, if the inflow of sludge whichmay cause contamination of the detecting section 162 increases in thedischarge pump tank 180 as the inflow of water into the discharge pumptank 180 increases, the discharge of water to be discharged from thebranch pipe 196 can be increased by that much, so that the effect ofwashing the detecting section 162 can be enhanced. By such control, thedetecting section 162 can be washed in an efficient manner in accordancewith the amount of sludge inflow.

Further, with regard to the water quality sensor 160, the sensor surfaceof the detecting section 162 may preferably be oriented to extend in adirection crossing the direction of discharge of the water to bedischarged from the branch pipe 196. In this construction, theorientation of the sensor surface of the water quality sensor 160 may beadjusted according to the direction of discharge from the pump dischargesection 176, or vice versa. With this construction, the discharge energyof the water discharged from the branch pipe 196 can be efficientlycaused to act upon the sensor surface of the detecting section 162, sothat the detecting section 162 can be washed by stronger water force.

Further, with regard to the construction of the discharge pump tank 180in this embodiment, instead of using the discharge pump 190 both forwater discharge and for sensor washing, the discharge pump 190 may beused exclusively for water discharge. In this case, the washingmechanism using the air lift pump 170 or the washing mechanism usingwater discharged from the discharge section 154 in the water treatmentapparatus 100 according to the first embodiment may be used to wash thewater quality sensor 160.

As described above, according to the water treatment apparatus 300 inthe second embodiment, the same effect can be obtained as the firstembodiment. Particularly, the detecting section 162 of the water qualitysensor 160 can be reliably washed by utilizing the force of waterdischarged from the branch pipe 196 of the discharge pump 190 in thedischarge pump tank 180. Thus, the water quality sensor 160 can attainhigher accuracy of water quality detection. Further, sludge contained insterilized water has lower adhesion than that in unsterilized water andis thus less sticky or viscous and resistant to adhesion to the waterquality sensor. Therefore, sludge or any other deposits can be furtherreliably prevented from being deposited on the detecting section 162 ofthe water quality sensor 160 submerged in the discharge pump tank 180.

This invention is not limited to the above-mentioned embodiments, butvarious applications or modifications may be made. For example, thefollowing embodiments may be provided by application of theabove-mentioned embodiment.

In the above-mentioned embodiment, the detecting section 162 is washedby using the construction in which water is pumped up by the air liftpump or the submerged pump and discharged toward the detecting section162 of the water quality sensor 160, or the construction in which wateris caused to fall from a height above the detecting section 162 of thewater quality sensor 160 toward the detecting section 162. However, inthis invention, other washing mechanisms may be used. For example, amovable member (such as a blade member) may be caused to rotate orreciprocate toward the detecting section 162 in the water in order toincrease the flow rate of the water flowing around the detecting section162 of the water quality sensor 160 and wash the detecting section 162.

Further, in the above-mentioned embodiment, a solid chlorinating agentis used for sterilization of the sterilizing tank 150. However, insteadof chlorination, other sterilizing methods, such as ozone sterilization,UV (ultraviolet) sterilization and electrolytic sterilization, may beappropriately employed.

Further, in the above-mentioned embodiment, turbidity (or transparency),a kind of water quality, is detected by using the water quality sensor160. However, in addition to or instead of turbidity (or transparency),it may be constructed such that the water quality can be detected interms of SS, BOD, DO or pH.

Further, in the above-mentioned embodiment, the air lift pump 170 isused exclusively for washing the water quality sensor 160. However, thepump discharge section of the air lift pump or submerged pump whichtransfers water in other location may branch and lead part of the waterto be discharged toward the water quality sensor so that the waterquality sensor 160 can be washed. In this case, the air lift pump or thesubmerged pump may be installed in the sae region as or in a differentregion from the submerged region of the water quality sensor. Further,in this invention, water flowing upstream or water flowing downstream ofthe submerged position of the water quality sensor may be used forwashing the water quality sensor.

Further, the present invention is applied to the water treatmentapparatus 100 having the foreign matter removing tank 110, the anaerobicfilter bed tank 120, the contact filter bed tank 130, the treated watertank 140 and the sterilizing tank 150 within the tank body 101, or tothe water treatment apparatus 300 having the foreign matter removingtank 110, the anaerobic filter bed tank 120, the contact filter bed tank130, the treated water tank 140, the sterilizing tank 150 and thedischarge pump tank 180 within the tank body 101. However, thisinvention can also be applied to a water treatment apparatus having atleast an aerobic treatment region in which water is aerobically treatedand a downstream region in which the water treated in the aerobictreatment region flows. In this invention, as the aerobic treatmentregion, a carrier flow biofiltration tank having movably packed carrierson which biomembrane of aerobic microbes is deposited, or an aerobicdigestion tank in which sludge is aerobically digested may be used aswell as a treatment tank such as the contact filter bed tank 130 of thisembodiment. Further, in this invention, the downstream region maycomprise a sterilizing tank for sterilizing water, or a storage tank fortemporally storing the sterilized water before discharged.

Further, this invention can also be applied likewise to variousindustrial wastewater treatment apparatus.

DESCRIPTION OF NUMERALS

-   100, 300 wastewater treatment apparatus-   101 tank body-   110 foreign matter removing tank-   120 anaerobic filter bed tank-   130 contact filter bed tank-   140 treated water tank-   150, 250 sterilizing tank-   151, 181, 251 submerged region-   152 chemical cartridge-   153 tub-   154 discharge section-   160 water quality sensor-   162 detecting section-   162 a light emitting section-   162 b light receiving section-   164 cable-   166 output section-   170 air lift pump-   172 pump body-   174 pump intake section-   176 pump discharge section-   178 air supply section-   180 discharge pump tank-   190 discharge pump-   191 pump body-   192 motor-   193 pump intake section-   194 transfer tube-   195 pump discharge section-   196 branch pipe-   197 water level sensor-   198 controller

1. A water treatment apparatus comprising: an aerobic treatment regionthat treats water aerobically, a sterilizing region in which the wateraerobically treated in the aerobic treatment region flows and issterilized, a water quality sensor that is submerged in the sterilizingregion and detects the water quality, and a sensor washing arrangementsubmerged in the sterilizing region that washes the water quality sensorby supplying the water of the sterilizing region to the water qualitysensor at a flow rate higher than water flowing around the water qualitysensor.
 2. The water treatment apparatus as defined in claim 1, whereinthe sensor washing arrangement includes a discharge section from whichthe water in the sterilizing region is discharged toward the waterquality sensor, wherein a drop is provided between the discharge sectionand the water quality sensor such that the discharge height of thedischarge section is higher than the installation height of the waterquality sensor, and wherein the water discharged from the dischargesection is supplied to the water quality sensor by the force of thedischarged water falling toward the water quality sensor at a flow ratehigher than water flowing around the water quality sensor.
 3. The watertreatment apparatus as defined in claim 1, wherein the sensor washingarrangement comprises a pumping device that pumps up water of thedownstream region through a pump intake section and discharges the waterthrough a pump discharge section toward the water quality sensor andwherein the sensor washing arrangement supplies the water dischargedthrough the pump discharge section to the water quality sensor by theforce of the water discharged toward the water quality sensor at a flowrate higher than water flowing around the water quality sensor.
 4. Thewater treatment apparatus as defined in claim 1, wherein the sensorwashing arrangement includes a controller that varies the amount ofwater to be discharged from the pump discharge section toward the waterquality sensor according to the operating duty of treatment regionslocated upstream of the installation location of the water qualitysensor.
 5. The water treatment apparatus as defined in claim 2, whereina sensor surface of the water quality sensor is oriented to extend in adirection crossing the direction of discharge of the water to bedischarged from the discharge section or the pump discharge section. 6.The water treatment apparatus as defined in claim 1, wherein the sensorsurface of the water quality sensor is smoothed.
 7. A water treatmentmethod using a water treatment apparatus including an aerobic treatmentregion in which water is aerobically treated, a sterilizing region inwhich the water treated in the aerobic treatment region flows and issterilized, and a water quality sensor that is submerged in thesterilizing region and detects the water quality, wherein: water in thesterilizing region is supplied to the water quality sensor at a flowrate higher than water flowing around the water quality sensor in orderto wash the water quality sensor by preventing deposition onto the waterquality sensor or removing deposits on the water quality sensor.